1. Field of the Invention
This invention relates to musical brass-wind instruments of the type employing piston valves, which includes trumpets, cornets, fluegelhorns, valve trombones, bass trumpets, baritone horns, alto horns, valved bugles, tubas, and sousaphones.
2. Description of the Prior Art
Designers of piston valved instruments have sought to attain the optimum shape of the air column therein contained in order to produce resonant frequencies most nearly matching the musically desirable frequencies of the tempered scale. The direction of research has been to reshaping the bell and leader pipe portions of the air column.
It is known in the art that an abrupt change of circular cross section of a tube introduces increased impedance and that the effect of such a discontinuity is to introduce an inductance in series with the standing waves of the air column, thereby producing a reinforced response in the instrument. It is also known that the playable intonation, here defined as the capability of an instrument to be easily adjusted in pitch by use of lip control and exitatory air flow changes at the player's embouchure and mouth cavity, is improved with increased oscillation of the air column.
Prior art teaches that the valves portion of the air column should present little or no discontinuity of bore. Slight constrictions and misalignments in the valve pistons have been cited as the cause of shortcomings in the performance of some instruments. In all known commercial trumpets the valve bore diameter is constant through the valves area and all valve pistons are aligned, with all piston and valve casing ports matching.